1. Field of the Invention
The present invention relates to an electromagnetic actuator having a coil, a stator core and a movable core.
2. Description of Related Art
In order to increase a maximum flow amount of a valve, it is necessary to increase a maximum opening degree of the valve, and to increase a stroke of a movable core of an electromagnetic actuator that operates the valve. However, a long stroke arrangement requires a wider gap between the movable core and a stator core. For example, when the movable core and the stator core face in a stroke direction, e.g. axial direction, of the movable core, widening the gap between the cores directly causes a reduction of the magnetic flux. Therefore, the electromagnetic actuator needs a larger coil with greater ampere-turn to attract the movable core against an urging spring over the increased stroke.